The present invention relates to drive mechanisms for conveyor belt systems and, more particularly, to a drive mechanism for a cage used in a spiral conveyor belt system.
Spiral conveyor belt systems are well-known in the art. They are commonly used in applications where it is desired to keep an item moving for an extended period of time within a contained environment, e.g., a product traveling through a refrigeration zone for cooling. As will be recognized by those skilled in the art, a spiral system typically consists of an endless conveyor belt traveling through concentric stacked helical paths whereby an item travels upward in elevation along the helical paths and/or downward in elevation along the helical paths.
Spiral systems typically utilize a cage (sometimes known as a “drum”) for driving the conveyor belt. More particularly, the cage is centrally positioned within the helical path, and includes a plurality of circumferentially-spaced vertical driving bars which contact the inner edge of the belt to impart a driving force thereto.
In many applications, the cage extends from and is supported by a centrally-located shaft. In turn, the shaft is rotatably supported upon a stationary frame. A drive mechanism is connected to the cage, and rotates the cage with respect to the frame. As the drive mechanism turns the cage, the cage contacts/drives the belt through the helical pathway of the conveyor belt system. Smaller cages often times utilize a center drive mechanism which directly communicates with the center shaft, resulting in rotation of the cage. Larger cages typically utilize a chain and tooth arrangement whereby the chain extends around the circumference of the cage and engages teeth located on the circumference of such cage. The chain in turn communicates with a drive motor.
Those skilled in the art will appreciate that prior art cages are typically constructed by welding together a plurality of individual pieces. This type of construction is time consuming, costly and requires tremendous levels of skill to ensure the “roundness” of the assembled cage. It will be appreciated that the roundness of a cage will affect the smoothness of the rotation, the engagement of the cage with the belt, and the engagement of the teeth on the cage with drive chain.
Prior art cages utilizing a chain and tooth arrangement typically mount the tooth segments on a vertically-extending outer wall of the cage. More particularly, the teeth are typically welded to an arcuate plate sized to be secured to the outer vertical wall of the cage. This type of arrangement, however, provides limited flexibility in installing the tooth segments to compensate for the “out-of-roundness” of the cage itself. Moreover, the tooth segment assemblies themselves may have issues with tolerances, which will also affect the smoothness of the rotation of the cage. Finally, the normal “stretching” which occurs in a chain after periods of operation often require substantial and costly modifications/remarks to the prior art cage.
There is therefore a need in the art for an improved drive mechanism for driving larger-sized cages in a spiral conveyor belt system. There is a further need in the art for a drive mechanism which can compensate for the “out-of-roundness” of the cage, and which can eliminate the hand fitting of tooth segments, and the welding and drilling associated therewith during both initial installation and normal maintenance due to “stretching” of the chain.